Intestinal Nematodes Flashcards
Concomitant immunity
Ability of a host to mount an effective defense against larval stages whilst being unable to clear a persistent burden of adult worms
Why is concomitant immunity good for the parasite?
Reduces competition within the host
Why is concomitant immunity good for the host?
Limits incoming parasite burden (preventing overwhelming infection)
Goblet cell
Specialised epithelial cell that produces mucus IgA
Three main components of the intestinal mucosal system
- Epithelium
- Lamina propria
- Organised lymphoid tissue
Crypt
Gland found in between villi in the intestinal epithelium lining that contains stem cells
Gastro-intestinal nematode infections
- Ascaris lumbricoides
- Trichuris trichiura
- Hookworms
Major classes of anti-helminthics for humans and animals
- Benzimidazoles (Albendazole, Mebendazole etc.)
- Nicotinic acetyl choline receptor inhibitors (Levamisole, Pyrantel, Oxantel)
- Inhibition of glutamate-gated chloride channels (Ivermectin)
Overdispersion
The idea that in most populations infected with worms, there is not normal distribution as most worms of the population are found in a small number of strongly infected individuals
Re-infection studies
•Treat individuals in an endemic area with anti-helminthic to clear worm burden
•Allow population to acquire new worm burdens naturally
•Re-assess worm burdens:
Correlation between pre-treatment and post-treatment worm burdens
Cytokines correlated with lower egg burden in Trichuris and Ascaris
IL-13 and IL-5
Mouse nematode infections
Nippostrongylus brasiliensis
Trichinella spiralis
Heligmosomoides polygyrus
Trichuris muris
Trichuris muris
- Whipworm, natural parasite of wild mice
- Exhibits overdispersion in the wild (outbred population) - some have high burdens just like in humans
- Morphologically, physiologically and antigenically similar to human counterpart Trichuris trichiura
- Direct life cycle (no intermediate host), only lives in caecum and colon
Key differences between normal and more susceptible mice
CD4 T cells
Th2 cytokines - IL-4 and IL-13
IL-25 responsive innate lymphoid cells (ILC2)
Innate lymphoid cells (ILC)
Innate counterparts of T cells that contribute to immune responses by secreting effector cytokines
